library(iNZight)
iNZight()

LoadDataWindow <- setRefClass("LoadDataWindow",
    fields = list(
        filename = "character"
    ),
    methods = list(
        initialize = function(...) {
            w <- gwindow("Load data")
            g <- ggroup(horizontal = FALSE, container = w)

            # Get filename from user
            fileedit <- gedit(container = g)

            # Load data
            loadbtn <- gbutton("Load", container = g)

            addHandlerKeystroke(fileedit,
                handler = function(h, ...) {
                    filename <<- svalue(h$obj)
                }
            )

            addHandlerClicked(loadbtn, function(h, ...) loadData())
        },
        loadData = function() {
            data <- read.csv(filename)
        }
    )
)

LoadDataWindow <- setRefClass("LoadDataWindow",
    fields = list(
        filename = "character"
    ),
    methods = list(
        initialize = function() { ... },
        loadData = function() {
            data <- read.csv(filename)
        }
    )
)

LoadDataWindow <- setRefClass("LoadDataWindow",
    fields = list(
        filename = "character",
        filetype = "character",
        delimiter = "character", # csv can use , or ;
        ...
    ),
    methods = list(
        initialize = function(...),
        loadData = function() {
            if (filetype == "csv") {
                data <- read.csv(filename, delimiter = delimiter, ...)
            } else if (filetype == "excel") {
                data <- readxl::read_xls(filename, ...)
            } else ...
        }
    )
)

LoadDataWindow <- setRefClass("LoadDataWindow",
    fields = list(
        filename = "character",
        filetype = "character",
        delimiter = "character", # csv can use , or ;
        ...
    ),
    methods = list(
        initialize(...),
        loadData = function() {
            data <- iNZightTools::smart_read(filename,
                filetype = filetype,
                delim = delimiter,
                ...
            )
        }
    )
)